My pet lamb 'Pirate' is so called because she has a patch of black
wool around one eye. Why do some white lambs get black patches of wool?

Dorian Garrick, an animal scientist at Massey University, responded.

When we spend time in the sunshine our skin gets darker as a result of a
pigment or paint in the skin known as melanin. This same pigment in sheep
makes their wool black.

Most sheep do not produce this pigment and all their
wool is white. Some sheep produce a lot of this pigment and are black all
over. Other sheep produce the pigment in small patches and appear piebald.
This may involve just one black patch (as for Pirate) or several black
patches.

Sheep can only produce black wool if their skin has the instructions or
recipe to make the melanin pigment. These instructions are known as genes.

A few white sheep carry the instructions for black colour or black patches
without showing any black wool. These sheep are said to carry a recessive
gene. When white sheep that carry the instructions for black patches are
mated together, some of their lambs will appear piebald with black patches.

Farmers, don't usually like sheep with black patches in their wood because
this wool when spun into yarn will have black or dark marks. These marks
will show up when the yarn is made into a jersey or carpet. Most farmers
will not keep sheep with black patches in their wool. However, unless these
farmers remove the parents of the piebald lambs, they are likely to have a
few more Pirates turning up in the future.